Knowledge of time in distant space operating regimes is fundamental to the scientific discovery, economic development, and international collaboration that form the basis of U.S. leadership in space. Today, the White House Office of Science and Technology Policy (OSTP) is releasing the first-ever U.S. government policy memorandum on time standards at and around celestial bodies other than Earth, building upon the Biden-Harris Administration’s National Cislunar Science and Technology Strategy.

“As NASA, private companies, and space agencies around the world launch missions to the Moon, Mars, and beyond, it’s important that we establish celestial time standards for safety and accuracy,” said OSTP Deputy Director for National Security Steve Welby. “Time passes differently in different parts of space—for example, time appears to pass more slowly where gravity is stronger, like near celestial bodies—and as a result the length of a second on Earth is different to an observer under different gravitational conditions, such as on the Moon. A consistent definition of time among operators in space is critical to successful space situational awareness capabilities, navigation, and communications, all of which are foundational to enable interoperability across the U.S. government and with international partners.”

A unified time standard—Coordinated Lunar Time (LTC)—will act as the established standard to enable cislunar operations and can be tied to Coordinated Universal Time (UTC), the primary time standard globally used to regulate clocks and time on Earth. This policy directs NASA to work with the Departments of Commerce, Defense, State, and Transportation to deliver a strategy for the implementation of LTC no later than December 31, 2026. NASA will also coordinate with other federal agencies as appropriate and international partners through existing international forums, including Artemis Accords partner nations.

More information and the full policy are available here.


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